The ultimate goal of this research is to develop a nonshrinking, high performance dental resin matrix material. The specific aims are: (1) to select the most promising alicyclic stereoisomeric spiroorthocarbonates (SOC) monomeric materials that have previously demonstrated expansion during polymerization (the basic monomer structure has been developed on the current NIH project); (2) to chemically modify these selected monomers for optimization of photoinitiated cationic polymerization; (3) to determine the reactive diluents required for optimization of the monomer formulation to form polymer/copolymers as matrix resins; and (4) to evaluate the physicochemical, mechanical, and initial biological characteristics of the new resin matrix formulations. The study has two phases. Phase I involves the utilization of the alicyclic SOCs developed on the present NIH grant. We have been successful in developing alicyclic stereoisomeric spiroorthocarbonates which expand during polymerization. These monomers are fairly well identified but require an optimization of properties through minor modification. The major objectives of phase I are to identify the SOC monomers which polymerize with the maximum volume expansion and to determine the effects of monomer modification on polymerization rate and solubility parameters. Phase II involves the development of an improved resin matrix material. The goals of this phase are to identify the compatibility of the SOCs with selected reactive diluents; to ascertain photoinitiators and sensitizers for their polymerization; and to determine the physicochemical properties of the resultant matrix resins. This proposal has been revised in compliance with suggestions made in the critique of the initial continuation application. We will concentrate on developing matrix resin materials and wait to formulate composites resins until we have completed the present project.